1. Field of Invention
The present invention relates to a method for manufacturing a field emission cathode and more particularly is directed to a method for manufacturing a field emission cathode microtip. The present invention is also directed to a field emission cathode having a large electron-emitting area which enables high electron emission and minimizes cathode tip erosion.
2. Description of Related Art
With the increasing demand for the popular use and miniaturization of displays which serve as the interface between human beings and computers or other computerized mechanisms, various flat screens or flat-panel displays have been developed for use instead of cathode ray tubes which are relatively large and difficult to handle. Such flat-panel displays include plasma display panels, liquid crystal panels, fluorescent display panels, field emission display panels, and the like. Among the flat-panel displays, the field emission display panel can be driven with low power consumption and may be easily used to produce color images.
The field emission display panel is constructed to emit electrons using a field emission array in which cathode tips are densely integrated as a field emission source for every unit pixel and also to converge the emitted electrons onto the phosphorous screen, and thereby form a picture or image.
The cathode tip is usually made of metal and is placed in a high-vacuum closed space which facilitates electron emission. Recently, according to the development of semiconductor device manufacturing technology, various manufacturing methods of microtips have been proposed using the same.
For instance, U.S. Pat. No. 4,513,308 to Greene et al. discloses a field emission cathode in which a pyramidal field emission cathode structure is placed on a monocrystal substrate using a P-N junction.
U.S. Pat. No. 3,970,887 to Smith et al. discloses a field emission cathode and a manufacturing method thereof in which a field emission tip is formed on the semiconductor substrate by thermal oxidation. According to this method of Smith et al., an oxide pattern mask is first formed on a silicon substrate by electron beam evaporation. The substrate is then thermally oxidized twice so that the masked portion and the unmasked portion receive different levels of thermal oxidization. The difference of thermal oxidation speeds forms an intended field emission tip.
In the method according to Smith et al., however, since the tip forming reaction is subject to and dependent on the concentration of a reaction gas, it is difficult to control the height of the field emission cathode tip as well as the sharpness of the tip. Further, this method has disadvantages during mass production because the forming of the pattern mask depends on and is limited by evaporation and photolithography.